Identity which statement is true: A. Isotopes of the same element have the same atomic number and mass number, but a different
number of neutrons.
B. Isotopes of the same element have the same mass number and different atomic numbers.
C. Isotopes of the same element have the same atomic number and different mass numbers.
D. Isotopes of the same element have the same number of neutrons and a different number of protons.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.